Thermal de-binding kinetics of injection molded W-8%Ni-2%Cu

The pre-mixed W-8%Ni-2%Cu with 50 vol% AIT binder specimens were fabricated by powder injection molding machine. The injected specimens were solvent de-waxed by dipping in n-heptane. Solvent de-waxed specimens were used to investigate thermal degradation of backbone at different heating rates by the mean of nano-balance coupled with mass spectrometry. The evolved products were captured and analyzed online by TG/MS. The heavy alloy shows catalytic effect on thermal decomposition of backbone binder. To investigate this catalytic effect, different metals feedstock were also analyzed and different mass loss behaviors were obtained. Studies show that tungsten metal has pronounced catalytic effect on backbone decomposition. By the help of degradation mechanism, the kinetic analysis was accomplished. Smooth thermal de-binding temperature–time profile was calculated under rate controlled de-binding conditions. The comparison was made between experiment and prediction in Elnik production furnace.     

Effect of processing technique on the transport and mechanical properties of vapour grown carbon nanofibre/rubbery epoxy composites for electronic packaging applications

Vapour grown carbon nanofibre (VGCNF)/rubbery epoxy (RE) composites were produced, by either mechanical mixing, three-roll milling (RM) or combined ultrasonication/mechanical mixing. Incorporation of VGCNFs resulted in significant enhancements in the thermal and electrical conductivities of the material. Appropriate selection of processing technique and parameters can help to maximise the potential of VGCNF additions by improving their dispersion in the matrix. The composites produced by RM have superior transport properties compared with those produced by other techniques. The thermal conductivity of such composites at 40 wt.% VGCNFs reached 1.845 W/m K, a 10-fold increase compared to RE alone. The thermal conductivity data of VGCNF/RE composites best fits to the Hatta–Taya model. The lowest electrical percolation threshold is at 2 wt.%, obtained for composites produced by RM. The thermal conductivity of VGCNF/glassy epoxy (GE) composites at 12 wt.% is 10% lower than the corresponding RE composite but its electrical conductivity is 2 orders of magnitude higher than the corresponding RE composite. VGCNFs at 40 wt.% increase the compressive strength of rubbery epoxy by ～5× but the compressive modulus of 40 wt.% VGCNF/RE composite is 12 times lower than that of 12 wt.% VGCNF/GE composite, demonstrating highly compliant nature of RE composites.     

Carbon black/graphite nanoplatelet/rubbery epoxy hybrid composites for thermal interface applications

Hybrid composites were developed by dispersing carbon black (CB) nanoparticles and graphite nanoplatelets (GNPs) at 4–6 and 12–14 wt%, respectively, into rubbery epoxy resin. SEM analysis showed that CB particles improved the dispersion of GNPs in the hybrid composite. The thermal conductivity of 4 wt% CB/14 wt% GNP-15/rubbery epoxy hybrid composite, 0.81 W/m K, is ca. four times higher than that of rubbery epoxy. When silane-functionalised, the fillers reduced the viscosity of the hybrid dispersion and made the hybrid composite highly electrically insulating. Nevertheless, filler functionalisation decreased the composite’s thermal conductivity by only 16.6%. Compression testing showed that the hybrid fillers increased the compressive modulus and strength of rubbery epoxy by nearly two and three times, respectively. Overall, the hybrid composites with their thermal paste-type morphology, low viscosity, high compliance, improved thermal conductivity and, when fillers are functionalised, low electrical conductivity makes them promising materials as thermal interface adhesives.     

Comparison of pneumatic retinopexy and scleral buckling in the management of primary rhegmatogenous retinal detachment. Southern Wisconsin Pneumatic Retinopexy Study Group

PURPOSE: To compare pneumatic retinopexy and scleral buckling for repair of primary rhegmatogenous retinal detachment with respect to visual outcome, single-procedure reattachment rate, and development of proliferative vitreoretinopathy. METHODS: A consecutive series of eyes initially treated with pneumatic retinopexy (n = 56) between March 1986 and February 1996 were compared with a selected group of eyes treated with scleral buckling (n = 86) with similar location and distribution of retinal breaks and absence of proliferative vitreoretinopathy. A regression model was developed to adjust for underlying differences between treatment groups, resulting in a cohort of 50 eyes in each group for final comparison. A minimum follow-up of 6 months was obtained. RESULTS: Single-procedure reattachment rate was significantly higher for scleral buckle eyes (42 of 50 eyes, 84%) than for pneumatic retinopexy eyes (31 of 50 eyes, 62%; P < or = .01). Correspondingly, reoperation rate was significantly higher for pneumatic retinopexy eyes (19 of 50 eyes, 38%) than for scleral buckle eyes (7 of 50 eyes, 14%; P < or = .01). Multiple regression analysis evaluating perioperative factors demonstrated that the use of pneumatic retinopexy was the sole factor predictive of retinal detachment after a single procedure (relative odds = 2.20, P = .02). Final reattachment rate, after reoperations, was 98% (49 of 50 eyes) in each group. Except for nonphakic eyes, final visual outcome and rate of postoperative proliferative vitreoretinopathy development did not differ significantly between the two procedures. CONCLUSIONS: In phakic eyes, pneumatic retinopexy was associated with a significantly higher reoperation rate than scleral buckling, but resulted in equivalent final visual outcome and reattachment rate after reoperations. If used, it must be incorporated into a strategy in which patient and physician are prepared for a greater chance of reoperation compared to initial management with scleral buckling.     

Phase Evolution and Microstructural Studies in CaZrTi2O7–Nd2Ti2O7 System

A series of compositions with general stoichiometry Ca_1?xZr_1?xNd_2xTi₂O₇ has been prepared by high‐temperature solid‐state reaction of component oxides and characterized by powder X‐ray diffraction and electron probe for microanalyses (EPMA). The phase fields in CaZrTi₂O₇–Nd₂Ti₂O₇ system and distribution of ions in different phases have been determined. Four different phase fields, namely monoclinic zirconolite, cubic perovskite, cubic pyrochlore, and monoclinic Nd₂Ti₂O₇ structure types are observed in this system. The 4M‐polytype of zirconolite structure is stabilized by substitution of Nd³⁺ ion. The addition of Nd³⁺ ions form a cubic perovskite structure‐type phase and thus observed in all the compositions with 0.05 ≤ x ≤ 0.80. Cubic pyrochlore structure‐type phase is observed as a coexisting phase in the nominal composition with 0.20 ≤ x ≤ 0.90. Only a subtle amounts of Ca²⁺ and Zr⁴⁺ are incorporated into the perovskite‐type Nd₂Ti₂O₇ structure. EPMA analyses on different coexisting phases revealed that the pyrochlore and perovskite phases have Nd³⁺‐rich compositions.     

Synthesis and characterization of PHV-block-mPEG diblock copolymer and its formation of amphiphilic nanoparticles for drug delivery

Despite the recent research interest in the field of nanoparticles delivery system, their structure modification and transport behavior of various hydrophobic drugs is poorly developed. In this article the synthesis of novel amphiphilic diblock copolymer poly([R]-3-hydroxyvalerate)-block-monomethoxy poly(ethylene glycol) (PHV-block-mPEG) was undertaken by modifying the structure of biodegradable and hydrophobic poly([R]-3-hydroxyvalerate) (PHV) with hydrophilic monomethoxy poly(ethylene glycol) (mPEG). The chemical combination of the two blocks was carried out in the melt using bis(2-ethylhexanoate) tin as transesterification catalyst. The synthesized product was characterized by gel permeation chromatography (GPC), 1H nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) analysis. The block copolymer self-assembled into amphiphilic nanoparticles with a core of hydrophobic PHV and a shell of hydrophilic mPEG in aqueous solution. Characterization of the nanoparticles showed the formation of discrete, spherically shaped nanoparticles with mean particle size of 200 +/- 1 nm and zeta potential of -14 +/- 1 mV. A hydrophobic drug thymoquinone was efficiently incorporated into the core hydrophobic domain of the nanoparticles and its release kinetics was studied in vitro. The amphiphilic PEGylated nanoparticles showed biocompatibility when checked in neuronal hippocampal cells of prenatal rat. Our results suggest that the amphiphilic nanoparticles with core-shell structures are potentially useful to develop novel drug carriers.     

Characterisation of graphite nanoplatelets and the physical properties of graphite nanoplatelet/silicone composites for thermal interface applications

Thermally conducting and highly compliant composites were developed by dispersing graphite nanoplatelets (GNPs) into a silicone matrix by mechanical mixing. X-ray diffraction (XRD) indicates that the average thickness of the GNPs decreased from 60 to 35 nm during mechanical mixing. XRD-texture analysis demonstrated that GNP/silicone composites at 8 wt.% GNPs have a higher degree of basal plane alignment than at 20 wt.%. Differential scanning calorimetry showed that GNPs raised the curing temperature of silicone with no significant effect on the glass transition temperature. The thermal conductivity of the 20 wt.% composites reached 1.909 W/m.K, an 11-fold increase over silicone suggesting an improved dispersion compared to similar composites prepared by dual asymmetric centrifuge mixing. The percolation threshold for electrical conductivity of the composites was at ∼15 wt.%. The compressive modulus of the composite increased to twice that of silicone at 20 wt.%. The corresponding strength decreased by a factor of two compared to silicone and this can be attributed to the weak bonding at the GNP-silicone interface. Overall, these GNP/silicone composites, with a high thermal conductivity, low electrical conductivity and compliant nature are promising materials for use as thermal pads for thick gap filling thermal interface applications.     

Dependence of magnetoelectric properties on the magnetostrictive content in 0–3 composites

The magnetoelectric response in composites of barium titanate (BTO) and cobalt ferrite (CFO) has been determined by measuring the magnetoelectric susceptibility coefficient. This was done by two different methods: magnetocapacitance measurements and magnetoelectric voltage measurement using a lock-in technique. These composites were prepared by the sol–gel method. Four different compositions with different molar ratios of the magnetostrictive phase (CFO) embedded in a piezoelectric matrix of BTO were studied to investigate the effect of the magnetostrictive content and the number density of interfaces on the magnetoelectric response. It was found from both techniques that the magnetoelectric coupling effect increases with the increase of applied field and it had a non-linear dependence on the percentage of magnetostrictive content in the composites.     

Chemical composition and antioxidant activity of quince fruit pulp collected from different locations

This study was carried out to examine the physicochemical and functional characteristics of quince fruit pulp. The matured quince fruits were collected from different locations of Poonch, AJ&;K, Pakistan. Significant differences (P ? 0.05) were found among fruits collected from these locations. The quince pulp has the following characteristics: pH (3.43), total soluble solids (14.22°Brix), acidity (1.25%), carbohydrate (13.38 g/100 g), reducing sugar (5.15 g/100 g), non-reducing sugar (4.61 g/100 g), moisture (84.27 g/100 g), ash (0.62 g/100 g), fat (0.24 g/100 g), protein (0.49 g/100 g), fiber (1.65 g/100 g), ascorbic acid (15.46 mg/100 g), and total phenolic (68.13 mg gallic acid equivalent/100 g) and antioxidant activity (50.05%). This exploration is the basic direction, which highlights the nutritional characteristics of quince fruit grown in AJ&;K, Pakistan.